The study aimed to characterize the sexual health, peer social networks, and social/cognitive associates of sexual health among migrant and non-migrant female Street Walkers (SW) in Shanghai, China. Shanghai is China's largest cargo port and a major metropolitan area [1]. It has 5 million rural-to-urban migrant population [2] and the highest sexually transmitted infection (STI) incidence rate [3-6] in China. The findings from this study will be used to guide the development of a future longitudinal sexual health risk reduction study targeting migrant and non-migrant street walkers. "Street walkers"(SW), who are at the bottom of the sex work hierarchy[13-15], were reported to be older, less educated, lower-paid, and less likely to use protection in sexual transactions compared to sex worker from other venues in our pilot study. They are also acknowledged by researchers and public health agencies to be extremely difficult to reach [7-9].Little is known about their sexual health (e.g. prevalence of STI, unprotected and other high-risk sexual behavior) and how they associated with the nature of their work (e.g., peer social network, group norm, gender-based relational power, and social provision). In addition, it is not clear how sexual practices differ between migrant and non-migrant street walkers. Interventions must be developed to target this high-risk population. To do so, it is critical to establish reliable and valid data regarding their determinants of risk and the context in which this occurs. It is the overarching goal of this proposed study. In the current application we Respondent Driven Sampling (RDS) will be used for the first time to recruit female street walkers in China (200 migrants vs. 100 non-migrants). The specific aims are to: (1) describe and compare the prevalence of unprotected sexual practices and STIs (Chlamydia, gonorrhea, syphilis, HSV-2, and HBV) between migrant and non-migrant street walkers;(2) describe and compare the characteristics of peer social networks of migrant and non-migrant street walkers based on formative qualitative interviews and RDS affiliation indices;and (3) test a working conceptual model relating unprotected sexual practices and STI prevalence to individual level social cognitive factors (e.g., perceived STI risk, self efficacy of consistent condom use, outcome expectancy of condom use) and contextual social cultural factors (e.g, gender-based sexual relationship power, peer social network, group norms) in the migrant and non-migrant street walker populations. The proposed study is significant as it focuses on a growing high-risk and under-studied population: street walkers in China. The project is innovative in its use of RDS for recruitment in this hard to reach population and in its assessment of peer social networks and their association with sexual health among both migrant and non-migrant street walkers. Findings from the proposed study will have far reaching implications for sexual health promotion and disease prevention / interventions, particularly those using "peer education" models, to target street walkers in China and elsewhere. PUBLIC HEALTH RELEVANCE: The primary goal of this 2-year study is to characterize the sexual health, peer social networks, and cognitive and social associates of sexual health among migrant and non-migrant female Street Walkers (SW) in Shanghai, China. Shanghai is one of the largest metropolitan areas in China and has the largest migrant population and the highest STI incidence rate of all Chinese cities. The findings from this study will be used to guide the development of a future longitudinal sexual health risk reduction study targeting street walkers.